Amplifier



April 16,1929. H MAYER 1,709,360

AMPLIFIER Filed March 29, 1927 lNVENTOR HANS M AYER A ORNEY Patented Apr. 16, 1929.

UNITED STATES' PAT'ENT X OFFICE.,

mms MAYEB, or .BERLIN, GERMANY, ASSIGNOR TO SIEMENS a EALSKE, .AKTIEN- GESELLSCHAFT, or SIEMENSSTADT, NEAR BERLIN, GERMANY, .A CORPORATION or GERMANY.

AMPLIFIER.

Application filed 'March 29, 1927, Serial N'o. 179,282, and in Germany March 27; 1926.

An application for this invention has been filed in Germany, March 27, 1926, No. 73,965.

In order to raise the efliciency of multi-stage resistance Coupled amplifiers, resistance coupled ampifiers with baek-couphng have been previously disclosed. In most of these schemes, the plate of a given tube 1s coupled with the grid of a preceding tube by way of a condenser, or a resistance. However, arrangements of this kind involve-a number of drawbacks. When using condensers for back-coupling, the degree of regenerative couphng and consequently the amplifieatlon factor of the arrangement depend markedly upon the frequency of the currents to be transferred so that the amplifier loses its property as a distortionless coupling means.

When usinga resistance for regenerative coupling, there-arises the difficulty that this resistance, for zero back-eouplmg, must. be of V infinitely large size, indeed, that it must be of very large size also for 'sueh other reaction coeliicients as may be needed 11'1 praet1ce (of an order of magnitude of 10 ohms) In the presence of resistances of such value, accurate adjustment of the latter is entirely out` of the question. Another demerit in the case of a kind of regeneration as he-reinbefore referred to is that the tube in question whose plate is in 0 back-coupling relation with the grid of a preceding tube, is connected in parallel to the input resistance of the grid of the first tube, in other words, to the secondary winding of the i input transformer at which the controlling electro-motive force is acting, with the result that, on applying the controlling electro-mox tive forces, currents are set up in the backcoupling circuit so that, upon Variation of a resistance, say, the input resistance of the am- 0 plifier, even if the controllim eleetro-motive 'force is kept at a constant vflue, undesirable fluetuntions of the back-coupling factor are brought about.

Now, the present invention obviates the said drawbacks. This is accomplished by that the back-coupling is not established between plate and grid, but rather between grid and grid,

in such a manner that the electro-motive force impressed upon the grid of the first tube is connected in series with the regenerative-coupling elemeht. Branched ofi from a backcoupling resistance of a tube in series with the ordinary grid leak, direct connection is established in this scheme with the grid of a tube 2, 4, 6 stages .below, This latter idea, namely, the omission of the intermediate tube, is resorted to on the ground that the potentials acting at the' grid of two adjacent or nei ghboring tubes presents a phase difference (phase angle) of 180 degrees so that the same is unsuited for back-coupling.

Since in this novel regeneration scheme as hercinbefore outlined no inductive or capacitive reaetances whatever are caused to arise (for the back-coupling resistance is free from capacity and inductance actions just like the other plate and grid resistances), this arr'angement offers reliable conditions for perfect freedom from frequency dependency and I perfect freedom from distortion.

The accompanying drawing by way of example shows an embodiment of this design of regenerative coupling. R are the plate resistances of tubes 1 to 3, C the eoupl ing con-' s1stance-capacity amplifier arrangement. In 7 densers, R the rid leaks of an ordinary re- .the grid circuit of tube in series with the grid resistance B there is the back-couplin'g Fil `resistance R The point connecting these two resistances by way of the alternating current potential source E .whose voltage is to be amplified, is united with the grid of the tube 1. The following Calculation will demonstrate the increase in amplification realizable by means of the'foregoing circuit arrangement: Denoting the grid alternating current potentials of the different tubes of the amplifier by E E E (the arrows in the drawing indicating the different directions of the currents at the same instant) and if W denotes the amplification factor of one tube of the regeneratively Coupled amplifier, then:

E WE', and 9:' Eg WU? 0 Application of the grid back-coupling the way as here shown then results in a growth in grid potential of the first tube to :g

' R i 1e0 I n E1 EnEa am,,

The increase in resistance in the first grid circuit (E by the value of the back-coupling resistance R may be disregarded in the calculation. Then, by adding the successive outpnts of the amplifier due to the successive feedbacks, for regenerative amplification the resultant output is given by a convergent series whose sum may beshown to be equal to:

As an example shall be cited the conditions for an amplifier tube resulting in an amplification factor=7, in the presence of a grid leak of R,,=6()00O Olllll. The first two tubes, in the absence of back-coupling (Rt- 0), then result in a potential amplificatlon of 7 7=49. Choosing a back-couphng resistance R =120O ohm, then, in the light of Equation (3), the potential amplification of the first two tubes becomes:

as contrasted with 49 without regeneration. For one stage, this means an ampl ficatlon of Hence, by means of regeneration it is possible to insure just as large an amplification as with transformer-coupled amplifiers, though the advantage is obtained over the transformer-eoupling scheme that operation is largely free from distortion.

If the alternating current potential of a current source is to be amplified and if one of the poles of the source is grounded, then, since the -latter is not united Withany filament, a convenient plan is to insert a transformer between the potential source and the input circuit of the amplifier.

I claim as my invention:

1. A regenerative system comprising a plurality of thermionic tubes, the feed back circuit of said system comprising a substantially pure resistance connection from the grid circuit of one tube to the input side of a preceding tube. v

2. A regenerative system comprising a plurality of vacuum tubes, the input circuit of said system comprising in series, a portion of the grid leak resistance of one of the grid circuits of one of the tubes of the system.

3. A regenerative system comprising a plurality of vacuum tubes and a Variable portion of the grid leak of one of the tubes in series with the input of a tube a multiple of two stages preceding the said one tube.

4. A regenerative system comprising a plurality of resistance coupled vacuum tubes, a pair of grids of separate tubes being conduc-, tively connected together for roviding a regenerative feed back, the gri s so connected together having controlling potentials of the same sign at any given instant.

5. A regenerative resistance coupled amplifier system comprising a first vacuum tube, a second vacuum tube and athird vacuum tube, the input to the first tube being fed through a Variable portion of a resistance in series with the grid of the third tube.

6. A regenerative system comprising a plurality of vacuum tubes and a connection between two of the tubes of the system for feeding back energy from one to the other of said two tubes, said connection connecting the grids of the two tubes. i

7 In a system for amplifying electrical impulses, a plurality of resistance cou led vacuum tubes, and conductive coup ing means between two grids of two of the tubes for providing a regenerative feed back.

HANS MAYER.

' Certificate of Correction Patent No. 1,709,360.

' HANS MAYER Granted April 16, 1929, to

It is hereby certified that. error appears in the printed specification of theabove numbered patent requirin r correction as follows: Page 1, strike out lines 75 and 76 and insert instead the sylla 1e and words dan ers, Rg the grid Zeaks of am ordinary &Stance-capacity amplifier awangement. I n, and that the said Letters Patent should be read with this correction therein that th case in the Patent Oflice.

e same may conform to the record of the Signed and Sealed this 11th day of February, A. D. 1930.

i sme M. J. MOORE,, a Acting Commissioner of Patent&

Certificate of Correction Patent No. 1,709,360. Granted April 16, 1929, to HANS MAYER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, strike out lines 7 5 and 76 and insert instead the syllable and words dan ers, R the gm'cl Zealcs of cm ordinary resistance-capacity amplifier arrangement. I n, and that thesaid Letters Patent should be read with this correction thei-ein that the same may conform to the record of the ,case in the Patent Oice.

Signed and Sealed this 11th day of February, A. D. 1930.

[SEAL] M. J. MOORE,

Acting Commissioner of Patent& 

